Method of manufacturing elastic fluid turbine buckets



Patented Jam, 1942 mamon or muvracruamo sms'rrc raum 'rmmr Rudolphllillner, General El New York aucxirrs seheneeiedy, N. r., 'mignontoeetrio Company, acorponon of- Appiieetion renom is. im, serial No; 251,5

4 chime. (i. sii-15er) o 1 'I 'his invention relates to elastic huid'turbine buckets and more particularly to removable bucket unitsforturbines of the axial now type and methods of manufacturing same.

In axial noweiestie nuid turbines desienedes for high admissionpressures, for example, of the order of 1200 pounds per square inch andabove, and correspondingly high initial temperatures, it is requiredthat the buckets, particularly vin n thehigh pressure stages, be of anextremelyfro strong and rigid #construction One form ofa suitable bucketarrangement consistsof a plurality of bucket units each having a baseportion, a plurality of blades and a heavy cover portion bleek or metaler blank. considerable. diiiieuityY is experienced in accurately formingthe lconcave and eon'vex surfaces denning the adjacent blade walls ofthe unit. This difficulty is primarily due to the particular arcuateconfiguration 'of `the passage which must be 'formed through the blank.from side in side. it beingof irregular shape and relatively narrow sothat suiilcient clearances do not existfor cutting tools of suilicientrigidity to be passed into the cavity from either side for removingmetaltherefrom in a satisfactory' manner. `In accordance with my "iiventigui,the passage defining the inner, adjacent walls of a pair of bladeportions is maall machined from4 a single piece of forged steel. '515chined out from the upper, or cover. end of the 'I'he base' of suchbucket unitmay be provided with. a dovetail slot for removablypositioning the unit onto the rotor rim. 'Ihe .manufacture of suchbucket units from solid blocks of metal blank.

l In Fig. 1 is shown a solid block of metal or Ablank I preferably offorged steel of a proper alloy which will give suiilcient strength andrigidis exceedingly diiiicult. in that accurately finished '20 ity tothe nished unit for withstanding the most transverse passages of arcuatecross-sectional shape must be formed through the block defining' theelastic uid channels between the adjacent'fblade portions.

It'isanfob'jct of this invention to provide a -25 new Tvand improvedelastic fluid turbine bucket unitihaving a plurality ofblades and baseand .cover portions rigidly connecting the opposite ends thereof.

It is a further object of this invention to pro- 3'0 vide a new andimproved method of manufacturing elastic vfluid turbine bucket unitscomprising abase portion, a plurality of blades and a cover portionintegrally united together in a rigid unit by which method the bladeportions can be manufactured with comparative ease andwith"great"aocuracy while the strength of the finished unit is such aswill withstand the most extreme conditions of turbine operation.

e For a consideration of .what I believe to be novel and my invention,attention is directed 'A to the following description and the claimsappended thereto taken in connection with the accompanying drawings.

'bucketinitmafactured in accordance with a methodv `ci.' lmy invention.

extreme conditions of operation when assembled in the high pressurestages of a turbine. o The iouter surfaces of the blank may befirstrough machined or'squared to some suitable preliminary shape,- suchas that shown. y The, upper end or portion, which willconstitute thecover for the bucket unit, is indicated at -i if; the base or lowerlportion in which the dovetailr fasteningmeans will be-formed'isindicated. at I2; while the interwill be formed is indicated at I3. Thebase portion i2 may be first slotted' as indicated at il in Figs. 3 and5 as a preliminary rough milling operation to the formation ofthedovetail which may becompleted later on in "the; sequence of themanufacturing steps. The rough slot I4 -is useful during the immediatelysucceeding steps in that the positioning of the blank in fthe workholder of the machine is thereby facilitated. In Fig. 2 is shown an endview of the'ablank having traced thereon in dotted lines'alayout-indicating a cross-section of a pair of blades i5 and'i dening anarcuately shaped passage il therev between which is to be milled out.Preliminary to the millingfof the passage itself, a chamfered groove ilsimilar in shape to the passage il is milled in the. .upper end portionil of the blank as shown in Fig. 3, 'I'he chamfered'sides of this grooveare desired for a later welding-operation The passage I1 is then formedby an en milling operation illustrated in Fig; 4 in which the mill- Inthe machining of turbine bucket units, eml -ing tool Il is shownextending downwardly into bodying a plurality of blades, from a singlesolid the blank through the upper end thereof and mediate section orportion from which the blades and also to enable an enlarged shankmilling.` tool to be used inthe machining of the assage.

parallel with the side Walis 'f adjacent concave and con of ltheadjacent blade pori tively, may 'ce formed` as operation may beperformer high degree of accuracy since may be of comparatively shoIierigth and such a diameter as .to be r at ely inflexible. Asis wellunderstood in the the adjacent surfaces of the blade portions are nottruly parallel but are slightly spread apart at the upper ends so as toconform with the radius of curvas ture of the turbine rotor rim.

The upper end of the passage il is then closed by welding a suitablyshaped insert 22 into the charnfered groove in the upper end or coverportion II-. The welded cover .portion reuniting the upper ends of .theblade portions is shown milling tc-ol i@ v rirn.

more clearly in Fig. 6, the welds are V-shaped in'oross section asindicated at`23. Because the welding operation is likely to set upinternal Astresses within the metal of the blank, it is pre ferred thatthe blank be heat treated or annealed at this stage in order that suchstresses be relieved before the manufacture of the unit progressesthrough the succeeding stages.

The remaining steps to be performed upon the 'blank present noparticular diillcultiesV and may be carried out by well-known methods byanyo'ne skilled in the art by simply machining or milling the remainingsurplus of metal `from the outer surfaces of the blank. The outerfconvexassenso bucket units having any greater number ,of blades. t is furtherunderstood that the dovetype of fastening arrangement shown is merelyillustrative of any suitable meansfcr mounting the bucket units upon theturbine rotar Having describec' the principle of operation of myinvention together with the apparatus' which now consider to representthe best em bodirnent thereof, I desire to have it understood that theapparatus shown is only illustrative and that the invention can becarried out by other means.

What I claim as new and desire to secure Letters Patent of the UnitedStates is:

l., The method of making an elastic fluid turbine bucket unit fromforged steel which comprises the steps of making a blank having lowerintermediate and upper portions, removing material from the upperportion to form a groove tapered towards the intermediate portion and ofy a width and curvature near the intermediate porand concave sides ofthe blade portions -IS and V I6 maybe milled olf leaving the cover andbase portions Il and I2 intact for separate machine operations to beperformed thereon. The dovc4 tailslot in the base portion Il may.thenben lcompleted giving itthe suitable curvatureI for fitting ontothe turbine rotor. vThe cover portion of the unit may be machined to theproper thickness in accordance with the' degree of ri'- gidity requiredfor the upper ends ofthe blade portions. The opposite sidesV of the unitmay be Y tapered in accordance with the radius of curvature of thevturbine wheel 'and properly finished in order that adjacent bucketunits will ilt snugly between the adjacent blades.

The nished bucket unit, as shown in Fig. 7, is of an extremely strongandA rugged construction, the lower ends of the Ablades being integrallyunited with the baseA and being relatively immovable with respect toeach other. The upagainst each other and withthe proper spacing i'V-shaped welds.

tion substantially equal to the width and curvature of a bucket passageto be produced thereafter, removn'materlalfrom the intermediate portionto detlne a curved bucket passage. forming a curved strip V-shaped incross section, and fusing the strip to the walls of the groove by l A2.A method of producing a turbine blade unit consisting of a plurality ofblades integral with a single root, comprising providing a blank ofrectangular cross-section; .said blank having side, end, top, and bottomfaces; forming a nuid passage in the top face thereof; said passagehaving its ends opening through the opposite side faces of the blank;permanently securing a.

shroud piece in'closing relation to the open top of the passage;heat-treating the structure to remove stresses therein; Aand machiningthe blank to nal form.

3. AA method of producing a turbine blade unit consisting of a pluralityof blades integral with a single root, comprising providing a blankofrectangular cross-section; said blank having side,

end, top and bottom faces; forming'a fluid passage in an end thereof;said passage having its ends opening through the oppositeifaces of theblank; welding a shroud piece in closing relation vto the open top ofthe passage; heattreating the structure to remove stresses therein; and

I machining the blank to final form.

per ends of the blades being integrally unitedv through the bridging.cover Vportion Il further insures the complete rigidity of the bladeswith respectto eachother, the bucket unit shown possessing substantiallythe same strength as regards distortional stresses Vas though the slotil extending between the adjacentzblade portions had been formedtherethrough from theopposite sides Without disturbing the integralcover portion.

Though the bucket unit shown and describedin this instance .is providedwith but twolbades. it is obvious that the method of this invention isequally applicable in the manufacture -of 4. A method of producing aturbine blade unit consisting of a plurality of blades integral with asingle root, comprising providing a blank of rectangular cross-section;said blank having side, end, top and bottom faces; milling a uid passagein an end thereof, said passage having its vends opening through theopposite faces oi the blank; forming a shroud piece to ft'in the opentop of the passage; welding said shroud piece to the walls of thepassage adjacent the upper edges of the latter; heat-treating thestructure to remove stresses therein resulting from the welding; andvmachining the blank to y Y final form.

RUDOLPH HILLNER.

